Here's one to watch: Consumerpedia.org It says it's for consumer information and allows user comments and the building of pages and navigation aswell. From the name, you can guess that it's very similar to Wikipedia.

From the about page

onsumerpedia has no built in category hierarchy, but rather uses a unique user-driven hierarchical tagging system. This lets users create and define the relationships between different topics, helping others easily discover and browse related information (this is similar to that mythical college campus that was initially built without sidewalks so that they could later be properly placed over the dirt paths created by actual foot traffic patterns).

Short version: the Consumerpedia system is designed so that it evolves based upon how actual users wish to use it, with the sole organizing principle being how helpful it is to others.